International Journal of Coal Geology最新文献

{"title":"Coalbed gas: A review of research directions from the past to the future as facilitated by bibliometrics","authors":"Romeo M. Flores ,&nbsp;Tim Moore","doi":"10.1016/j.coal.2024.104683","DOIUrl":"10.1016/j.coal.2024.104683","url":null,"abstract":"<div><div>This bibliometric review used coalbed gas articles published in the International Journal of Coal Geology (IJCG) from 1986 to 2022 catalogued in the Scopus database to compare similar articles indexed in the Web of Science (WoS) database from 1999 to 2016. Comparison focused between highly cited articles (top 1 % versus &gt;100 citations in the WoS and Scopus databases, respectively) from the 2007–2016 period. Analysis of articles in the WoS database reveals research fronts center on modeling fractal pores related to gas adsorption and gas exploration in China's basins (Luo et al., 2017). In contrast, this study of research fronts of articles in the Scopus-IJCG database range from laboratory methods and models of coal reservoir properties; enhanced coalbed methane recovery and carbon dioxide storage; to experiments on microbes, methanogenesis, isotope geochemistry, and biochemical nutrients for biogenic gas generation. Thus, a key difference in coalbed-gas research fronts between the databases is disciplinary breadth for Scopus and discipline specific for WoS.</div><div>Caveats in interpreting analysis of citation numbers about research fronts include high rate of self-citation (“clubbing/inwardness”); researchers maintaining “continuous stream of publications for long periods”; growth of highly cited research of narrow fields with large datasets used to publish for prolonged periods; mass publications (“salami slicing”) to increase citation counts; researchers publishing in high-profile journals indexed by WoS for professional advancement; and experimental methods and review papers more cited than original papers. Also, the fall of gas prices from 2008 to 2014 facilitated rapid decrease in coalbed gas production and caused significant drop in the number of articles published in the IJCG from the United States and Europe. Conversely, the number of coalbed-gas articles from 2008 to 2022 increased 7–52 % for China and 25–33 % for Australia. Finally, analysis of IJCG articles reveals international research collaboration (IRC) grew up to 70 % by 2011 and became more diversified in research topics by 2022. Thus, IRC is the future pathway that brings together researchers to advance new knowledge of coalbed gas such as deep coalbed gas reservoirs to support Just Energy Transition as countries changeover to energy mix that moves away from coal to attain net-zero carbon emissions by 2050.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"298 ","pages":"Article 104683"},"PeriodicalIF":5.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142975197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry of tonsteins and its implications for Li-Zr (Hf)-Nb (Ta) enrichments in Cisuralian coal seams, Shanxi Province, North China","authors":"Zhanming Guo ,&nbsp;Beilei Sun ,&nbsp;Chao Liu ,&nbsp;Mingyuan Lei ,&nbsp;Xu Wang ,&nbsp;Yao Wang","doi":"10.1016/j.coal.2025.104697","DOIUrl":"10.1016/j.coal.2025.104697","url":null,"abstract":"<div><div>Altered volcanic ashes within coal and coal-bearing sequences, often occurring as persistent bands embedded within coal seams (generally as tonsteins), can characterize the geochemical features and hence quality of coal. This study investigates the mineralogical and geochemical features of tonsteins within the coal seams from Shanxi Formation, North China in order to define the critical elements enrichments in coal benches. Mineralogical analysis indicates that the tonsteins are predominantly composed of kaolinite and quartz, while illite was identified in one tonstein sample and some parting/floor samples. The geochemical data indicate enrichments in SiO₂, Al₂O₃, and CaO, while tonsteins display higher SiO₂/Al₂O₃ ratios than partings/floor and coals. Compared with world hard coals, the coal benches are enriched in Zr, Hf, Pb, and Th. These critical metals enrichments in coal benches are attributed to the volcanic ash input during peat accumulation. Hierarchical clustering of trace, major, and REY elements shows distinct grouping patterns between coal and non-coal samples. Group A3 clusters trace elements Li, Zr, Hf, Nb, and Ta together with major element oxides Al₂O₃ and SiO₂, and is primarily related to ash yield. The TiO₂/Al₂O₃ ratios, discrimination diagrams of Zr/TiO₂ vs. Nb/Y and Al₂O₃/TiO₂ vs. Nb/Yb ratios as well as REY distribution patterns, indicated that the tonsteins, transformed from air-fall volcanic ash, were likely derived from volcanic eruptions in Inner Mongolia Paleo-Uplift (IMPU), with volcanic ash of intermediate rock composition. The enrichment of critical metals, particularly Li-Zr (Hf)-Nb (Ta) assemblage, is primarily influenced by the input of multiple layers of intermediate volcanic ash during peat accumulation in the Cisuralian coal, North China.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"300 ","pages":"Article 104697"},"PeriodicalIF":5.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"","authors":"James C. Hower","doi":"10.1016/j.coal.2025.104698","DOIUrl":"10.1016/j.coal.2025.104698","url":null,"abstract":"","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"300 ","pages":"Article 104698"},"PeriodicalIF":5.6,"publicationDate":"2025-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Climatic reconstruction of the Late Palaeocene using sedimentary archives from the Bikaner-Nagaur Basin, Rajasthan, India","authors":"Dinesh Kumar ,&nbsp;Tushar Adsul ,&nbsp;Ofentse M. Moroeng ,&nbsp;Zoremsiami Pachuau ,&nbsp;Ashutosh Panigrahi ,&nbsp;Santanu Ghosh ,&nbsp;Asmita Datta ,&nbsp;Rupayan Sen ,&nbsp;Atul Kumar Varma","doi":"10.1016/j.coal.2025.104695","DOIUrl":"10.1016/j.coal.2025.104695","url":null,"abstract":"<div><div>The present study examines Late Palaeocene climatic changes recorded in the shale-lignite‑carbonaceous shale sequence of the Bikaner-Nagaur Basin, Rajasthan, India. Various analytical methods such as organic petrography, stable isotopes of organic carbon (δ¹³C_org), organic carbon to total nitrogen ratio (C_org/TN), Rock-Eval parameters, and Fourier transform infrared spectroscopy are employed to investigate the palaeoclimatic shifts. From the bottom shale to the overlying lignite sequence, δ¹³C_org shows minimal fluctuations, indicating a consistent supply of organic matter from both angiosperms and gymnosperms. However, a significant negative carbon isotopic excursion (nCIE; δ¹³C_org ranging from −26.8 to −29.9 ‰) is observed from the lignite to the overlying carbonaceous shales. This suggests a sudden increase in isotopically lighter CO₂ or its higher partial pressure in the atmosphere during the Late Palaeocene. This nCIE is accompanied by a sharp decrease in the C_org/TN values and a notable increase in ash yield for the carbonaceous shales, suggesting peatland flooding by sediment-laden surface runoffs triggered by intense precipitation. The increased rainfall also raised groundwater levels, stabilizing hydrological balance within the mire. This facilitated the selective preservation of hydrogen-rich alginite under anoxic conditions, as indicated by geochemical proxy (relative hydrocarbon potential = 4.52, on average), contributing to elevated hydrogen index values (443 mg HC/g TOC on average) in the carbonaceous shale samples. The increased groundwater level is linked with the observed nCIEs in the carbonaceous shale samples, suggesting an abrupt climatic transition characterized by ¹³C-depleted atmospheric CO₂ and intensified rainfall under warm-humid conditions during the deposition of these carbonaceous shales. These findings point towards potential influences of a Late Palaeocene global-scale hyperthermal event.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"299 ","pages":"Article 104695"},"PeriodicalIF":5.6,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143050020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Climatically-driven cessation of coal formation in tropical Pangea around the Pennsylvanian-Permian boundary; an example from alluvial-lacustrine succession of the Líně Formation (Czechia)","authors":"Roland Nádaskay ,&nbsp;Stanislav Opluštil ,&nbsp;Karel Martínek ,&nbsp;Zbyněk Šimůnek ,&nbsp;Jaroslav Zajíc ,&nbsp;Jana Drábková ,&nbsp;Petra Podzimková ,&nbsp;Ivana Sýkorová","doi":"10.1016/j.coal.2025.104694","DOIUrl":"10.1016/j.coal.2025.104694","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Increasing climatic seasonality within tropical Pangea during the Pennsylvanian–Permian transition had a significant impact on landscape habitat and terrestrial biota evolution. One of the important consequences was cessation of peat formation in tropical Pangea – an underexplored issue because successions of this age in major European coalfields are either not preserved or are stratigraphically poorly constrained. The about 1 km thick Líně Formation (upper Gzhelian–lower Asselian) of Bohemian basins dominated by fluvial and alluvial red-beds interbedded by grayish lacustrine deposits records ∼3.5 Myr long tectono-sedimentary, climatic and biotic history already calibrated by TIMS ages to the Pennsylvanian–Permian transition. By integrating outcrop- and basins-scale data on sedimentary facies as well as on terrestrial biota, this paper evaluates the effects of climate and of post-orogenic tectonic processes on resulting depositional and biotic records and their effect on peat accretion. The current data indicate that the climate oscillated in about 450 kyr scale between less and more seasonal. During the Late Pennsylvanian, minimum seasonality (max. humidity) supported presence of ‘wet fluvial systems’ and meromictic lake formation lined with rheotrophic peat swamps, whereas during the driest climate (max. seasonality), well-drained fluvial landscape dominated the basin lowland. During the Early Permian, well-drained fluvial/small shallow lake habitats (‘dry fluvial systems’) prevailed due to long-term aridification trend in tropical Pangea, and wetland – dryland biomes coexisted over most of the time in a preservation window of the basin lowland and/or adjacent upland habitats. Their proportion, however, varied significantly in accord with climatic oscillations. The Líně Fm. was deposited in a half-graben basin system formed in response to post-Variscan intra-plate extension. The basin filling reflected three ‘rift phases’: (1) initiation, with localized subsidence and opening of initial sub-basins; (2) climax, with more distributed, maximum subsidence and interconnecting of sub-basins to form extensive basin system; (3) waning, likely dominated by thermal subsidence.&lt;/div&gt;&lt;div&gt;Formation of major, basinwide Klobuky Lake was facilitated by wet period ocurring during the rift climax stage with the most rapid creation of the accommodation space. Peat swamps formed and the peat accreted only during the late Gzhelian up to TIMS calibrated C&lt;img&gt;P boundary. Increasing aridification, however, constrained peat swamps from floodplain to shallowed lakes, the water table of which suffered less from seasonal oscillations comparing to floodplain areas. Purely rheotrophic, usually high-ash peat swamps formed. The peat-swamp development was often interrupted by temporary rise of lake level and influx of clastic material. Resulting coal beds are usually few tens of centimeters thick, and if thicker, they commonly contain clastic partings or high-ash c","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"300 ","pages":"Article 104694"},"PeriodicalIF":5.6,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic evolution and differential enrichment of deep coalbed methane: A case study in Qinshui Basin","authors":"Xiongxiong Yang ,&nbsp;Shuheng Tang ,&nbsp;Zhaodong Xi ,&nbsp;Songhang Zhang ,&nbsp;Qian Zhang ,&nbsp;Ke Zhang ,&nbsp;Donglin Lin ,&nbsp;Jing Wang","doi":"10.1016/j.coal.2025.104696","DOIUrl":"10.1016/j.coal.2025.104696","url":null,"abstract":"<div><div>Gas content is a critical factor in evaluating the resource potential and predicting the productivity of deep coalbed methane reservoirs. This study investigates the evolution of gas content in deep coal reservoirs over geological time and explores models of differential gas enrichment. Using Carboniferous-Permian deep coal reservoirs in the Yushe-Wuxiang block of the Qinshui Basin as a case study, fluid inclusion analysis, basin modeling, and theoretical gas content calculations were combined to quantitatively reconstruct the pressure and gas content evolution during the uplift of these coal reservoirs. Fluid inclusion analysis revealed homogenization of temperatures ranging from 85 °C to 155 °C in the coal-bearing strata, indicating trapping pressures between 33.16 MPa and 46.42 MPa. These inclusions were trapped between 228.05 and 216.09 million years ago, coinciding with the period of maximum burial depth, and exhibit a pressure coefficient of 1.05–1.19, confirming an overpressure state. During the uplift phase, decreasing temperature and pressure led to the conversion of free gas into adsorbed gas. This transition resulted in a gradual increase in adsorbed gas content while free gas content declined. Intense tectonic activity during the Himalayan orogeny induced fracturing and depressurization of the coal reservoirs, causing substantial dissipation of free gas. Consequently, the deep coal reservoirs in the Yushe-Wuxiang block currently exist at normal pressure and are devoid of free gas. Comparative analysis of gas content and reservoir pressure evolution across different blocks led to the proposition of four distinct coalbed methane enrichment models: (1) deep burial and weak tectonic reworking, (2) deep burial and intense tectonic reworking, (3) shallow burial and weak tectonic reworking, and (4) shallow burial and intense tectonic reworking. The deep burial and weak tectonic reworking model are identified as a promising target for coalbed methane exploration and development in North China. This study elucidates the mechanisms responsible for differential gas content enrichment in deep coal reservoirs, providing valuable insights for guiding the exploration and development of deep coalbed methane resources.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"299 ","pages":"Article 104696"},"PeriodicalIF":5.6,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143049662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Matrix permeability anisotropy of organic-rich marine shales and its geological implications: Experimental measurements and microscopic analyses","authors":"Yong Ma ,&nbsp;Huiting Hu ,&nbsp;Zhejun Pan ,&nbsp;Ningning Zhong ,&nbsp;Fujie Jiang ,&nbsp;Chengyu Yang ,&nbsp;Jianbin Ma ,&nbsp;Binhao Feng","doi":"10.1016/j.coal.2024.104670","DOIUrl":"10.1016/j.coal.2024.104670","url":null,"abstract":"<div><div>Due to the presence of natural and/or preparation-related fractures, the anisotropy of the matrix permeability of shales is usually difficult to characterize. In this study, we used X-ray micro-computed tomography (XRμCT) imaging to select samples from the Lower Cambrian and Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation of the Upper Yangtze Platform, China, showing no natural or artificial fractures. From these samples, cubic specimens were prepared with a wire saw and then re-inspected for fractures. Using a specially developed sample holder, the matrix permeability of these specimens were measured in the three principal directions using the pulse decay method with N₂ as the flowing fluid. To analyze the microscopic lithological and structural controls on shale matrix permeability anisotropy, we employed a combined methodology using thin sections, focused ion beam-scanning electron microscopy (FIB-SEM), and permeability simulation.</div><div>The matrix permeability of the 15 shale samples ranged from 19.6 to 189.4 nD (19.6–189.4 × 10⁻²¹ m²) parallel to bedding and from 2.4 to 24.7 nD (2.4–24.7 × 10⁻²¹ m²) perpendicular to bedding, at a constant confining pressure of 1500 psi (10.3 MPa). Tectonic stress resulting from structural deformation leads to the deformation of OM pores within solid bitumen, which is the main factor controlling the matrix permeability. The ratio of the matrix permeability coefficients parallel and perpendicular to bedding (k_x/k_z) varied from 3.4 to 29.6, primarily due to cleavage zones along the bedding-parallel platy mica and clay altered from mica. The matrix permeability ratio in the two orthogonal horizontal directions (k_x/k_y) typically did not exceed a value of 2, but for samples with oriented graptolites and siltstone layers ratios as high as 2.9 and 2.3, respectively, were observed. The microfractures between graptolite and minerals, together with the elongated pores within the graptolites, enhance the permeability and facilitate gas flow along the bedding planes. The higher proportion of brittle minerals in siltstone renders it more prone to cracking compared to shale, which causes the anisotropy in the parallel-to-bedding directions.</div><div>For three shales from the strongly deformed northeast Chongqing with high-angle fractures parallel to the lamination, permeability parallel to bedding varied between 627.2 and 6820.3 nD, while permeability perpendicular to bedding ranged between 11.3 and 27.8 nD. The presence of microfracture parallel to the lamination in three shale samples resulted in a permeability higher by factors of 34 to 348 than the matrix permeability, leading to a higher anisotropy ratio between both horizontal and vertical directions.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"297 ","pages":"Article 104670"},"PeriodicalIF":5.6,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142825341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Staged evolutionary features of the aromatic structure in high volatile A bituminous coal (hvAb) during gold tube pyrolysis experiments","authors":"Wenbin Yang ,&nbsp;Pal Toth ,&nbsp;Yu Song ,&nbsp;Wu Li","doi":"10.1016/j.coal.2024.104660","DOIUrl":"10.1016/j.coal.2024.104660","url":null,"abstract":"<div><div>Low-temperature pyrolysis of coal is a crucial step in the coal thermal conversion process and involves very complex physical and chemical reactions that can have different effects on the coal's structure. The thermal evolution behavior and transformation mechanism of the coal microstructure are not yet fully understood, which also limits the efficient utilization of coal to a certain extent. The aromatic structural features (including size, molecular ordering, nematic symmetry, stacking, and curvature) of the char produced from low-temperature pyrolysis of high volatile A bituminous coal (hvAb) from the Xutuan coal mine, China, were quantitatively assessed via high-resolution transmission electron microscopy (HRTEM) image processing and analytical techniques. The thermal transformation process and the mechanisms controlling it were explored. The results show that, except for the unexpected slight growth of aromatic sheets at 440 °C, the lower pyrolysis temperature (&lt; 521 °C) contributed weakly to their size growth, whereas at higher temperatures (561–600 °C), it significantly increased their size. The aromatic molecular ordering tended to gradually change in three stages: increasing between 340 and 440 °C, decreasing between 440 and 521 °C and increasing again between 521 and 600 °C. The nematic symmetry strength of aromatic fringes also followed a similar pattern with temperature at different scales. Additionally, in addition to a very minor development trend at 440 °C, the stacking did not significantly change at temperatures below 521 °C but developed appreciably further with increasing temperatures at 561–600 °C; however, the average spacing of the stacks did not appear to be significantly reduced at all temperatures. The curvature of the aromatic sheets also varied in different temperature stages, i.e., initially slightly increasing (340–380 °C), then gradually decreasing (380–480 °C), later increasing again (480–521 °C), and eventually decreasing (521–600 °C). The properties of the chemical composition and structure of the initial coal play important roles in the thermal reaction behavior, and the physical and chemical reactions that dominate at the different temperature stages may be responsible for such wiggly trends in the evolution of the aromatic structure. Notably, the properties of the mesophase (approximately 440 °C) strongly influence the subsequent structural transformation. These findings could provide useful information for the microstructure–property relationships and preparation of coal-based carbon materials.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"297 ","pages":"Article 104660"},"PeriodicalIF":5.6,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142874792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Noble gases in Paleozoic shale fluids document tectonic events and fluid migration in the Upper Yangtze Block","authors":"Rui Liu ,&nbsp;Tao Wen ,&nbsp;Daniele L. Pinti ,&nbsp;Rui Xu ,&nbsp;Fang Hao ,&nbsp;Shang Xu ,&nbsp;Zhiguo Shu","doi":"10.1016/j.coal.2024.104671","DOIUrl":"10.1016/j.coal.2024.104671","url":null,"abstract":"<div><div>Major and noble gases of natural gas extracted from the low-permeability Paleozoic Wufeng-Longmaxi shale were measured to reconstruct the multi-stage, spatially varying tectonic evolution of the Upper Yangtze Block, China, one of the oldest parts of the Earth continents. The high gas dryness ratio [C₁/(C₂ + C₃)] and high carbon isotopic ratios (δ¹³C-C₁, δ¹³C-C₂, δ¹³C-CO₂) suggest a late mature thermogenic origin of shale gas. The highly fractionated atmospheric ²⁰Ne/³⁶Ar and ⁸⁴Kr/³⁶Ar ratios in our gas samples suggest they result from solubility-based partitioning of noble gases between oil and water followed by gas-water partitioning. Calculated volume ratios of oil, water, and gas phases vary spatially and temporally. In particular, the western Yangtze Block shows a lower reconstructed oil/water ratio, suggesting oil leakage promoted by the Triassic exhumation of Paleozoic shale, while a low gas/water ratio in the central-eastern Yangtze Block suggests gas leakage promoted by basin-wide Jurassic fold-thrust faulting. The lowest C₁/³⁶Ar volume ratio around faults at the basin edges indicates extensive gas expulsion. Delineated radiogenic ⁴He in gas samples are several orders lower than calculated in-situ produced radiogenic ⁴He, likely suggesting widespread ⁴He loss. Spatially-varying ⁴He/nucleogenic ²¹Ne ratios in the shale indicated that ⁴He loss in the western Yangtze Block predated that in the central-eastern portion. Such He loss was also coupled with the Triassic exhumation and the Jurassic fold-thrust faulting episodes. In summary, noble gas in pore fluids extracted from low-permeability shale can preserve reliable records of tectonic events produced during upper crust evolution.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"297 ","pages":"Article 104671"},"PeriodicalIF":5.6,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142874791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Elemental geochemical insights into sediment sources, influx variations and depositional environment changes in the Eocene–Miocene Lark Formation, Danish North Sea","authors":"Zhiheng Zhou ,&nbsp;Qingyong Luo ,&nbsp;Niels Hemmingsen Schovsbo ,&nbsp;Henrik Ingermann Petersen ,&nbsp;Arka Rudra ,&nbsp;Hamed Sanei","doi":"10.1016/j.coal.2024.104673","DOIUrl":"10.1016/j.coal.2024.104673","url":null,"abstract":"<div><div>The Lark Formation in the Danish North Sea holds great paleoenvironmental interest for understanding climatic and tectonic impacts on sediment supply and depositional environment during the latest Eocene to the Middle Miocene. This study investigates sediment provenance, variations in sediment flux, chemical weathering intensity, and redox conditions in relation to these climatic and tectonic events. A dataset of 86 cuttings and one core from six wells in the Danish North Sea was analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The recently published maceral composition of these samples was also included in this research.</div><div>Provenance investigation indicates that the sediment originated from felsic sources within a continental arc tectonic setting. Such a source area is currently located in southern Norway and Sweden on the southwest margin of the Baltic Shield. During the Eocene–Miocene progressive filling of the eastern North Sea Basin, climatic conditions primarily controlled chemical weathering intensity and sediment influx. This is evidenced by higher Chemical Index of Alteration (CIA) and Zr concentrations in the Lower Miocene compared to other series deposited under cooler and less humid climates. Additionally, elemental proxies (Ce_anom, V/(V + Ni), Th/U), along with organic petrological and geochemical evidence, indicate that the Lark Formation was deposited in dysoxic-anoxic environments. Variations of these proxies further reveal that sea-level changes primarily controlled fluctuations in redox condition, resulting in more oxic environments. Moreover, the impact of marine productivity on U and Mo is revealed by the positive correlations between the enrichment factors of U (U_EF) and Mo (Mo_EF) and the abundances of liptinite and Cd. Increased productivity, combined with bottom water anoxia, led to the enrichment of U and Mo in the sediment, with upwelling further enhancing this process.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"297 ","pages":"Article 104673"},"PeriodicalIF":5.6,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142901786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}